Mitral valve prolapse (MVP) has emerged as a prominent, predisposing structural cardiac abnormality and in adults accounts for 7 to 30 per cent of NVE in cases not related to drug abuse or nosocomial infection. This increased risk of endocarditis is largely confined to patients with both prolapse and a mitral regurgitation murmur. Risk is also increased among men and patients older than 45 years. Valve redundancy and thickened leaflets (> 5mm) by echocardiography also identify a population at increased risk for IE.